Setting up Units across multiple Floors

We are implementing Oracle property and as a landlord we provide units that spans across multiple floors. For ex. if the tenant is a big clothing store that has units across multiple floors. What is the best way to setup these units.

Option 1

Should we setup separate unit on the each floor in Oracle property and then setup the lease and include all these units.If we do this, how do we setup billing lines, do we have to setup billing line for each unit ? The lease may not have breakdown for individual units on each floor.

Option 2

Set up a single unit on only one floor and include area from other units on other floors into the setup of this unit. This way there is no need of setting up different billing lines as there is only a single unit.But this approach may not describe the property structure correctly.